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11 Oct 2010

Volume 97, Issue 15, Articles (15xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 97, 154101 (2010); http://dx.doi.org/10.1063/1.3479052 (3 pages)

Younggeun Park, Yeonho Choi, Debkishore Mitra, Taewook Kang, and Luke P. Lee
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Tensile strained island growth at step-edges on GaAs(110)

P. J. Simmonds and M. L. Lee

Appl. Phys. Lett. 97, 153101 (2010); http://dx.doi.org/10.1063/1.3498676 (3 pages) | Cited 4 times

Online Publication Date: 11 October 2010

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We report the growth of tensile strained GaP islands on a GaAs(110) surface. Three-dimensional island formation proceeds via a step-edge nucleation process. To explain the dislocation-free nature of these islands, we consider the kinetics of strain relief within the context of a model for dislocation glide as a function of surface orientation and sign of strain.
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68.55.ag Semiconductors
62.20.F- Deformation and plasticity
68.60.Bs Mechanical and acoustical properties
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
81.40.Jj Elasticity and anelasticity, stress-strain relations

Graphene as a transparent conductive support for studying biological molecules by transmission electron microscopy

R. R. Nair, P. Blake, J. R. Blake, R. Zan, S. Anissimova, U. Bangert, A. P. Golovanov, S. V. Morozov, A. K. Geim, K. S. Novoselov, and T. Latychevskaia

Appl. Phys. Lett. 97, 153102 (2010); http://dx.doi.org/10.1063/1.3492845 (3 pages) | Cited 26 times

Online Publication Date: 11 October 2010

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We demonstrate the application of graphene as a support for imaging individual biological molecules in transmission electron microscope (TEM). A simple procedure to produce free-standing graphene membranes has been designed. Such membranes are extremely robust and can support practically any submicrometer object. Tobacco mosaic virus has been deposited on graphene samples and observed in a TEM. High contrast has been achieved even though no staining has been applied.
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87.15.B- Structure of biomolecules
87.64.Ee Electron microscopy

Reduction of gate hysteresis above ambient temperature via ambipolar pulsed gate sweeps in carbon nanotube field effect transistors for sensor applications

Moritz Mattmann, Daniel Bechstein, Cosmin Roman, Kiran Chikkadi, and Christofer Hierold

Appl. Phys. Lett. 97, 153103 (2010); http://dx.doi.org/10.1063/1.3499363 (3 pages) | Cited 2 times

Online Publication Date: 11 October 2010

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We investigate the hysteresis behavior in carbon nanotube (CNT) field effect transistors (CNFETs) upon pulsed gate voltages (Vg) above ambient temperature within 300–390 K. Assuming charge trapping near the CNT channel to be the major mechanism behind gate hysteresis, we perform charge trapping experiments based on Vg pulses and find that CNFET charge trapping is increasing with temperature. We assess the impact of thermally enhanced charge trapping on the hysteresis reduction performance of two different pulsed Vg sweeps. One of the two sweeps, consisting of alternating polarity pulses, is shown to essentially eliminate gate hysteresis in the studied temperature range.
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85.30.Tv Field effect devices
85.35.Kt Nanotube devices

rf plasma oxidation of Ni thin films sputter deposited to generate thin nickel oxide layers

Megan L. Hoey, J. B. Carlson, R. M. Osgood, III, B. Kimball, and W. Buchwald

Appl. Phys. Lett. 97, 153104 (2010); http://dx.doi.org/10.1063/1.3499661 (3 pages) | Cited 5 times

Online Publication Date: 11 October 2010

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Nickel oxide (NiO) layers were formed on silicon (Si) substrates by plasma oxidation of nickel (Ni) film lines. This ultrathin NiO layer acted as a barrier layer to conduction, and was an integral part of a metal-insulator-metal (MIM) diode, completed by depositing gold (Au) on top of the oxide. The electrical and structural properties of the NiO thin film were examined using resistivity calculations, current-voltage (I-V) measurements and cross-sectional transmission electron microscopy (XTEM) imaging. The flow rate of the oxygen gas, chamber pressure, power, and exposure time and their influence on the characteristics of the NiO thin film were studied.
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81.65.Mq Oxidation
73.61.At Metal and metallic alloys
68.55.-a Thin film structure and morphology
81.15.Cd Deposition by sputtering

Different growth rates for catalyst-induced and self-induced GaN nanowires

C. Chèze, L. Geelhaar, B. Jenichen, and H. Riechert

Appl. Phys. Lett. 97, 153105 (2010); http://dx.doi.org/10.1063/1.3488010 (3 pages) | Cited 8 times

Online Publication Date: 12 October 2010

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The catalyst- and self-induced pathways of GaN nanowire growth by molecular beam epitaxy are compared. The catalyst-induced nanowires elongate faster than the self-induced ones and their growth rate is fully determined by the impinging N rate. The self-induced nanowire growth rate is identical on both Si(111) and Si(001) and approaches the impinging N rate only for the few longest nanowires. This difference is attributed to the presence of the Ni-catalyst which enhances the incorporation of Ga at the nanowire tip while for the self-induced nanowires, growth is limited by the different incorporation rates on the nanowire tip and sidewall facets.
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68.65.La Quantum wires (patterned in quantum wells)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
61.46.Km Structure of nanowires and nanorods (long, free or loosely attached, quantum wires and quantum rods, but not gate-isolated embedded quantum wires)
62.20.F- Deformation and plasticity
81.16.Hc Catalytic methods
81.40.Lm Deformation, plasticity, and creep

Atomistic simulation of plasticity in silicon nanowires

Fabrizio Cleri, Tadashi Ishida, Dominique Collard, and Hiroyuki Fujita

Appl. Phys. Lett. 97, 153106 (2010); http://dx.doi.org/10.1063/1.3501987 (3 pages) | Cited 3 times

Online Publication Date: 12 October 2010

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We study the tensile deformation of polycrystalline Si nanowires by means of molecular dynamics simulations. The initial microstructure is composed by a network of nanocrystals glued together by a thin layer of amorphous material. Atomistic simulations could clearly identify liquidlike flow in the constrained amorphous Si as the responsible for the observed elongation. After this first stage of nearly constant-stress flow, a necking instability sets in, eventually leading to fracture, at the point when the nanowire diameter becomes comparable to the size of the nanocrystals.
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81.40.Lm Deformation, plasticity, and creep
62.20.fq Plasticity and superplasticity
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.25.Mn Fracture/brittleness
81.05.Cy Elemental semiconductors

Surface segregation of bimetallic alloys in nanoscale confinement

Ming Hu, Konstantinos P. Giapis, Javier V. Goicochea, and Dimos Poulikakos

Appl. Phys. Lett. 97, 153107 (2010); http://dx.doi.org/10.1063/1.3500825 (3 pages) | Cited 2 times

Online Publication Date: 12 October 2010

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The surface segregation of Pt atoms in liquid bimetallic alloys confined in carbon nanotube cavities was studied using molecular dynamics simulations. Considerable enrichment in the Pt-atom surface density was found to occur in Pt alloys, when the complementary metal has surface energy higher than Pt and simultaneously metal-wall interaction strength lower than that of Pt with the confining wall. The results suggest that solidification of liquid binary alloys in nanochannels could produce core-shell nanorods with the shell enriched in one of the components for catalytic and other applications.
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68.35.Dv Composition, segregation; defects and impurities
81.30.Fb Solidification
64.70.D- Solid-liquid transitions

Growth of seaweed-like TiO2 nanoarrays for dye-sensitized solar cells

Hari Bala, Lei Jiang, Wuyou Fu, Guangyu Yuan, Xiaodong Wang, and Zongrui Liu

Appl. Phys. Lett. 97, 153108 (2010); http://dx.doi.org/10.1063/1.3497075 (3 pages) | Cited 3 times

Online Publication Date: 12 October 2010

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Seaweed-like titanium dioxide (TiO2) nanoarrays (STNAs) were grown on the surface of a titanium (Ti) sheet by hydrogen peroxide sculpture at low temperature. After calcination, the STNA transformed to highly crystalline anatase phase and exhibited a vertically standing structure, with an average length of 1.35–2.12 μm, leaves breadth of about 30–80 nm, and leaves thickness of about 10–15 nm. STNA-electrode dye-sensitized solar cells (DSCs) fabricated with dye C106 achieved an efficiency of 3.2% under irradiation of 100 mWcm‒2 air mass 1.5 global (AM1.5G) sunlight. Further research showed that the STNA-electrode DSC has much lower recombination rate (Kr) and longer electron life time (τn), thus making this STNA a potential candidate of electrode for fabricating high performance DSC.
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88.40.jr Organic photovoltaics
88.40.hj Efficiency and performance of solar cells
81.07.Bc Nanocrystalline materials
81.16.-c Methods of micro- and nanofabrication and processing
73.63.Bd Nanocrystalline materials
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Nonmonotonic crystallite-size dependence of the lattice parameter of nanocrystalline nickel

J. Sheng, U. Welzel, and E. J. Mittemeijer

Appl. Phys. Lett. 97, 153109 (2010); http://dx.doi.org/10.1063/1.3500827 (3 pages) | Cited 2 times

Online Publication Date: 12 October 2010

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A nonmonotonic crystallite-size dependence of the lattice parameter of ultrathin, nanocrystalline Ni films, i.e., lattice contraction followed by lattice expansion with decreasing crystallite size, was observed using in situ x-ray diffraction stress measurements combined with a dedicated thermal treatment called “loop annealing.” The expected lattice contraction with decreasing crystallite size was found for nanocrystalline Cu and nanocrystalline Pd.
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68.55.-a Thin film structure and morphology
61.72.Cc Kinetics of defect formation and annealing
61.46.Hk Nanocrystals
68.60.Bs Mechanical and acoustical properties

Surface enhanced resonance Raman and luminescence on plasmon active nanostructured cavities

Frances Lordan, James H. Rice, Bincy Jose, Robert J. Forster, and Tia E. Keyes

Appl. Phys. Lett. 97, 153110 (2010); http://dx.doi.org/10.1063/1.3500836 (3 pages) | Cited 8 times

Online Publication Date: 12 October 2010

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Presented here are studies of the impact of excitation angle on surface enhanced Raman and luminescence spectroscopy of dye immobilized on a plasmon active nanocavity array support. Results show that both Raman and luminescence intensities depend on the angle of incidence consistent with the presence of cavity supported plasmon modes. Dependence of scattering or emission intensity with excitation angle occurs over the window of observation.
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78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
78.30.Jw Organic compounds, polymers
78.55.Kz Solid organic materials

Mapping emissive channels of quantum dots: Influence of size and environment on energy transfer in the time domain

E. Faulques, F. Massuyeau, Q. Wang, D.-K. Seo, and S. Jobic

Appl. Phys. Lett. 97, 153111 (2010); http://dx.doi.org/10.1063/1.3497269 (3 pages) | Cited 2 times

Online Publication Date: 12 October 2010

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In the quantum confinement regime, the time-resolved photoluminescence mapping of CdSe nanocrystals reveals unusual size-dependent characteristics in solute or solid-state environments. The former case typifies long-lived intradot exciton recombinations, while in the latter energy-dependent Kohlrausch relaxations quench luminescence via interdot energy transfer. The observed energy transfer rate increases for larger size (1.5×108 s−1 for d = 2.5 nm and 6.4×108 s−1 for d = 10 nm).
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78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
71.35.-y Excitons and related phenomena
61.46.Hk Nanocrystals
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

First and second-order Raman scattering in Si nanostructures within silicon nitride

Lucia V. Mercaldo, Emilia M. Esposito, Paola Delli Veneri, Giuseppe Fameli, Salvo Mirabella, and Giuseppe Nicotra

Appl. Phys. Lett. 97, 153112 (2010); http://dx.doi.org/10.1063/1.3501133 (3 pages) | Cited 7 times

Online Publication Date: 12 October 2010

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First and second-order Raman analysis on annealed silicon nitride films is reported. Possible formation of amorphous Si nanoparticles after an intermediate treatment is deduced from the occurrence of a resonant spectrum. After nucleation of Si nanocrystals, with a model description of the first-order spectra it is possible to access information regarding mean radius, size dispersion, and crystalline phase fraction consistent with the fundamental data derived from microscopy. Substantial increase in second to first order intensity ratio is also observed: Enhanced electron–phonon coupling in both amorphous and crystalline Si nanoparticles is suggested.
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78.30.-j Infrared and Raman spectra
78.66.Db Elemental semiconductors and insulators
81.40.Gh Other heat and thermomechanical treatments
81.07.Ta Quantum dots
81.05.Cy Elemental semiconductors
63.20.kd Phonon-electron interactions

Influence of aggregation on thermal conductivity in stable and unstable nanofluids

P. D. Shima, John Philip, and Baldev Raj

Appl. Phys. Lett. 97, 153113 (2010); http://dx.doi.org/10.1063/1.3497280 (3 pages) | Cited 11 times

Online Publication Date: 12 October 2010

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We study the effect of nanoparticle aggregation on thermal conductivity (k), viscosity (η) and size distribution of a stable and unstable nanofluid of iron oxide (Fe3O4) and copper oxide (CuO), respectively. The k, η, and size are found to be time independent in Fe3O4 while they are time dependant in CuO nanofluid. The microscopic study shows a progressive increase in the size of aggregate from nano to micron in CuO nanofluid. Our results show the prominent role of agglomeration on thermal properties and the importance of surface functionalization for improved stability and performance of nanofluids.
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47.85.Np Fluidics
47.61.Fg Flows in micro-electromechanical systems (MEMS) and nano-electromechanical systems (NEMS)
66.25.+g Thermal conduction in nonmetallic liquids
66.20.-d Viscosity of liquids; diffusive momentum transport

Carrier transport in nanocrystalline field-effect transistors: Impact of interface roughness and geometrical carrier trap

Koshi Okamura and Horst Hahn

Appl. Phys. Lett. 97, 153114 (2010); http://dx.doi.org/10.1063/1.3495798 (3 pages) | Cited 6 times

Online Publication Date: 13 October 2010

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Nanocrystalline field-effect transistors (FETs) inherently have a certain level of roughness at the semiconductor-dielectric interface which originates from the size of nanocrystals. This interface roughness is expected to act like carrier traps, significantly preventing induced carriers from being transported along the channel in the FETs. In this study, a simple numerical calculation is performed for nanoparticulate ZnO FETs with the induced carriers classified into two components: (1) fixed carriers located within a threshold depth dth from the interface and (2) mobile carriers located away from dth. This calculation reveals that an interface roughness as small as a few nm results in a decrease in field-effect mobility as large as an order of magnitude, which is in qualitative agreement with experimental results.
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85.30.Tv Field effect devices
68.35.Ct Interface structure and roughness
72.20.Fr Low-field transport and mobility; piezoresistance
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.63.Bd Nanocrystalline materials
02.60.-x Numerical approximation and analysis

Rainbow trapping and releasing by chirped plasmonic waveguides at visible frequencies

Lin Chen, Guo Ping Wang, Qiaoqiang Gan, and Filbert J. Bartoli

Appl. Phys. Lett. 97, 153115 (2010); http://dx.doi.org/10.1063/1.3502487 (3 pages) | Cited 12 times

Online Publication Date: 13 October 2010

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We report on “trapping rainbow” on silver films covered by a one-dimensional chirped dielectric grating. We attribute the trapping effect to correlative dispersive relation between the excited surface plasmon polaritons (SPPs) and the lattice constant of the dielectric grating on the metal film, which results in localization of SPPs of different frequencies at different spatial positions. We further reveal that, by attaching another uniform dielectric grating on the other side of the metal film and real time tuning the refractive index of the grating, the trapped rainbow can be released in sequence. Analytical results are demonstrated by finite-difference time-domain simulation.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
42.79.Dj Gratings
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
02.30.-f Function theory, analysis
42.79.Gn Optical waveguides and couplers

Permalloy-based carbon nanotube spin-valve

H. Aurich, A. Baumgartner, F. Freitag, A. Eichler, J. Trbovic, and C. Schönenberger

Appl. Phys. Lett. 97, 153116 (2010); http://dx.doi.org/10.1063/1.3502600 (3 pages) | Cited 4 times

Online Publication Date: 13 October 2010

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In this paper we demonstrate that permalloy (Py), a widely used Ni/Fe alloy, forms contacts to carbon nanotubes (CNTs) that meet the requirements for the injection and detection of spin-polarized currents in carbon-based spintronic devices. We establish the material quality and magnetization properties of Py strips in the shape of suitable electrical contacts and find a sharp magnetization switching tunable by geometry in the anisotropic magnetoresistance (AMR) of a single strip at cryogenic temperatures. In addition, we show that Py contacts couple strongly to CNTs, comparable to Pd contacts, thereby forming CNT quantum dots at low temperatures. These results form the basis for a Py-based CNT spin-valve exhibiting very sharp resistance switchings in the tunneling magnetoresistance, which directly correspond to the magnetization reversals in the individual contacts observed in AMR experiments.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.47.-m Magnetotransport phenomena; materials for magnetotransport
72.15.Gd Galvanomagnetic and other magnetotransport effects
75.60.Jk Magnetization reversal mechanisms
72.25.-b Spin polarized transport
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.

Low temperature sintering of Ag nanoparticles for flexible electronics packaging

A. Hu, J. Y. Guo, H. Alarifi, G. Patane, Y. Zhou, G. Compagnini, and C. X. Xu

Appl. Phys. Lett. 97, 153117 (2010); http://dx.doi.org/10.1063/1.3502604 (3 pages) | Cited 19 times

Online Publication Date: 13 October 2010

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We achieve robust bonding of Cu wires to Cu pads on polyimide with silver nanopaste cured at 373 K. The paste is prepared by simply condensing Ag nanoparticle (NP) solution via centrifuging. The bonding is formed by solid state sintering of Ag NPs through neck growth and direct metallic bonding between clean Ag–Cu interfaces. Both experiment and Monte Carlo simulation confirm that the melting point of joint clusters increases during sintering. This creates improved bonds for use at an elevated operating temperature using Ag NPs.
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85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
02.70.Uu Applications of Monte Carlo methods

Defected graphene nanoribbons under axial compression

M. Neek-Amal and F. M. Peeters

Appl. Phys. Lett. 97, 153118 (2010); http://dx.doi.org/10.1063/1.3496467 (3 pages) | Cited 12 times

Online Publication Date: 13 October 2010

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The buckling of defected rectangular graphene nanoribbons when subjected to axial stress with supported boundary conditions is investigated using atomistic simulations. The buckling strain and mechanical stiffness of monolayer graphene decrease with the percentage of randomly distributed vacancies. The elasticity to plasticity transition in the stress-strain curve, at low percentage of vacancies, are found to be almost equal to the buckling strain thresholds and they decrease with increasing percentage of vacancies.
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61.48.Gh Structure of graphene
61.72.jd Vacancies
62.20.mq Buckling
81.40.Lm Deformation, plasticity, and creep
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity

Middle-ultraviolet laser photoelectron emission from vertically aligned millimeter-long multiwalled carbon nanotubes

Parham Yaghoobi, Mario Michan, and Alireza Nojeh

Appl. Phys. Lett. 97, 153119 (2010); http://dx.doi.org/10.1063/1.3496486 (3 pages) | Cited 3 times

Online Publication Date: 13 October 2010

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We demonstrate photoelectron emission from millimeter-long forests of vertically aligned multiwalled carbon nanotubes using 266 nm light, which illuminates the forests from the side. We have measured quantum efficiencies in the order of ∼ 10−5 at low fields (pure photoemission) and ∼ 10−3 at an applied field of 0.3 V μm−1, which are 2–4 orders of magnitude higher than those obtained from films of randomly oriented nanotubes, and approach the quantum efficiency of semimetal photocathodes. Through optical simulations we show that 266 nm light is absorbed within the first few layers of the nanotube forest.
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79.60.Jv Interfaces; heterostructures; nanostructures
78.67.Ch Nanotubes
73.63.Fg Nanotubes

Parylene-C passivated carbon nanotube flexible transistors

Selvapraba Selvarasah, Xinghui Li, Ahmed Busnaina, and Mehmet R. Dokmeci

Appl. Phys. Lett. 97, 153120 (2010); http://dx.doi.org/10.1063/1.3499758 (3 pages) | Cited 4 times

Online Publication Date: 13 October 2010

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Carbon nanotubes are extremely sensitive to the molecular species in the environment and hence require a proper passivation technique to isolate them against environmental variations for the realization of reliable nanoelectronic devices. In this paper, we demonstrate a parylene-C passivation approach for CNT thin film transistors fabricated on a flexible substrate. The CNT transistors are encapsulated with 1 and 3 μm thick parylene-C coatings, and the transistor characteristics are investigated before and after passivation. Our findings indicate that thin parylene-C films can be utilized as passivation layers for CNT transistors and this versatile technique can be readily applied for the encapsulation of CNT devices such as field effect transistors, p-n diodes, and logic circuits fabricated on flexible substrates.
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85.35.Kt Nanotube devices
85.30.Tv Field effect devices

Coexistence of strong ferromagnetism and polar switching at room temperature in Fe3O4–BiFeO3 nanocomposite thin films

E. Weal, S. Patnaik, Z. Bi, H. Wang, T. Fix, A. Kursumovic, and J. L. MacManus Driscoll

Appl. Phys. Lett. 97, 153121 (2010); http://dx.doi.org/10.1063/1.3500826 (3 pages) | Cited 5 times

Online Publication Date: 13 October 2010

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10% Fe3O4–90% BiFeO3 nanocomposite thin films of 180 nm thickness were grown by pulsed laser deposition on SrTiO3 (011) single crystals. A 3–4 nm nanolamella structure of Fe3O4 and BiFeO3 was formed. While BiFeO3 has the expected epitaxial relationship with the substrate, Fe3O4 grew epitaxially and highly strained (7%). Compared to pure Fe3O4 films of similar thickness, the nanolamella structure of Fe3O4 gives rise to a greatly enhanced saturation magnetization of 900 emu/cc, and, after field cooling, an enhanced coercivity of 450 Oe. Piezoresponse force microscopy measurements show similar polar switching properties between the nanocomposite and pure BiFeO3 films.
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81.07.Bc Nanocrystalline materials
77.80.Fm Switching phenomena
75.50.Dd Nonmetallic ferromagnetic materials
75.75.Cd Fabrication of magnetic nanostructures
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
77.55.hn Other piezoelectric or electrostrictive films

Pigtailed CdS nanoribbon ring laser

Yaoguang Ma (马耀光), Xiyuan Li (李西远), Zongyin Yang (杨宗银), Huakang Yu (虞华康), Pan Wang (王攀), and Limin Tong (童利民)

Appl. Phys. Lett. 97, 153122 (2010); http://dx.doi.org/10.1063/1.3501969 (3 pages) | Cited 4 times

Online Publication Date: 14 October 2010

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We demonstrated a pigtailed nanoribbon ring laser constructed with a 600 nm wide and 330 nm thick CdS nanoribbon. When the 20-μm-diameter ring was irradiated by light from a supercontinuum source, multi longitudinal mode laser emission was observed around 523.5 nm with full widths at half maximum of 0.27 nm. The laser output from the pigtail showed strong orientation-dependent polarization, with a maximum polarization ratio of 5 and power up to 3.7 nW.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.79.-e Optical elements, devices, and systems

Carbon nanotube stabilized conductive polymers

Yi-Fan Li, I-Sing Wong, Tao-Cheng Lai, Wei Chin, and Wen-Kuang Hsu

Appl. Phys. Lett. 97, 153123 (2010); http://dx.doi.org/10.1063/1.3502490 (3 pages) | Cited 1 time

Online Publication Date: 14 October 2010

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Carbon nanotubes act as radical scavengers in UV-irradiated conductive polymer (poly3,4-ethylenedioxythiophene:polystyrene sulfonate) and effect is verified by conductivity, electron paramagnetic resonance, and infrared absorption data.
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73.63.-b Electronic transport in nanoscale materials and structures
78.30.-j Infrared and Raman spectra
76.30.-v Electron paramagnetic resonance and relaxation
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures

Thermotropic nematic and smectic order in silica glass nanochannels

Andriy V. Kityk and Patrick Huber

Appl. Phys. Lett. 97, 153124 (2010); http://dx.doi.org/10.1063/1.3502595 (3 pages) | Cited 2 times

Online Publication Date: 14 October 2010

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Optical birefringence measurements on a rodlike liquid crystal, octyloxycyanobiphenyl, imbibed in silica channels (7 nm diameter), are presented and compared to the thermotropic bulk behavior. The orientational and positional order of the confined liquid evolves continuously at the paranematic-to-nematic and sizeably broadened at the nematic-to-smectic order transition, respectively, in contrast to the discontinuous and well-defined second-order character of the bulk transitions. A Landau–de Gennes analysis reveals identical strengths of the nematic and smectic ordering fields (imposed by the walls) and indicates that the smectic order is more affected by quenched disorder (originating in channel tortuosity and roughness) than the nematic transition.
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61.30.Eb Experimental determinations of smectic, nematic, cholesteric, and other structures
64.70.mj Experimental studies of liquid crystal transitions
78.15.+e Optical properties of fluid materials, supercritical fluids and liquid crystals

Dual-mode sensing platform based on colloidal gold functionalized porous silicon

Yang Jiao, Dmitry S. Koktysh, Nsoki Phambu, and Sharon M. Weiss

Appl. Phys. Lett. 97, 153125 (2010); http://dx.doi.org/10.1063/1.3503608 (3 pages) | Cited 5 times

Online Publication Date: 14 October 2010

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We report a dual-mode sensing platform based on a single layer porous silicon (PSi) film impregnated with colloidal gold nanoparticles. This gold-coated PSi film supports both quantification of molecular binding via reflectance measurements and molecular identification via surface enhanced Raman scattering (SERS). A detection sensitivity of approximately 400 nm/RIU was demonstrated through binding of benzenethiol molecules. Identification of the unique SERS peaks was possible with uniform signal intensity across the sample and a detection limit below 1 μM.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
78.68.+m Optical properties of surfaces
78.66.-w Optical properties of specific thin films
78.30.-j Infrared and Raman spectra
82.70.Dd Colloids
82.80.Gk Analytical methods involving vibrational spectroscopy
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